Programmable controller

Abstract

While a microcomputer is executing a self-diagnosis (A), second diagnosis pulse output means of a B-system microcomputer is not used utterly. Further, during this time, the B-system microcomputer 100B does not execute a processing relating to at least the self-diagnosis (A) utterly. By shifting the timings for the A-system and the B-system to output the diagnosis pulses, independencies can be secured between respective diagnosis processing (self-diagnoses (A) and (B)). Thus, the independencies between the A-system and the B-system can be verified briefly by the self-diagnosis (A) on the A-system side. Further, first diagnosis pulse group are outputted parallel and simultaneously from first diagnosis pulse output means. Thus, since cyclic control is not required for respective external input devices, it can be done to verify the independencies between the A-system and the B-system within a short period of time.

Description

TECHNOLOGICAL FIELD[0001]The present invention relates to a sequence control for the operations of a robot, a machine tool and peripheral devices therefor and particularly, is very useful in highly securing the reliability and safeness in the processing for input signals inputted to a programmable controller (PLC).BACKGROUND ART[0002]There is a system wherein a programmable controller performs the sequence control like that aforementioned above. In recent years, there is becoming widespread a PLC (so-called safety PLC) of an independent construction which is specialized for the safety management of the system in detecting the abnormality and the emergency state of the system as well as in automatically performing an emergency safety stop of the system. Patent Documents 1 and 2 noted below exemplify technologies relating to a so-called safety PLC like this.[0003]As one of other technologies, FIG. 14 exemplifies a circuit diagram (in normal state) of a known input circuit 201 which is...

AI Technical Summary

Benefits of technology

[0020]The present inventions in the following various aspects are effective in solving the aforementioned problems.

[0026]This invention in the second aspect is constructed to take two in the number of multiplexing. Respective systems take symmetrical circuit constructions. As is the same with the invention in the first aspect, the diagnosis pulses are outputted to the other system, and an abnormality judgment is executed by detecting the state of the input signal group in the system which parallel outputted the diagnosis pulses. Where a switch being an input device is brought into open state with the aforementioned short-circuit fault occurring and when the diagnosis pulses are inputted to interrupt electric current flowing through the circuit for the period of the diagnosis pulses, electric current flowing through the other circuit is also interrupted. By judging the state of the input signal group from the other circuit which is not inputting the diagnosis pulses thereinto, it can be realized to detect an abnormal state. In this detection, since the diagnosis pulses are parallel outputted to the input terminal group, it becomes possible to complete the abnormality diagnosis after the delay which is caused by the processing time of the input signal group subsequent to the output timing. Therefore, it becomes possible to perform an emergency stop without any delay after the change of an abnormality stop switch from the closed state to the open state. Strictly, the delay time at this occasion becomes a time which is taken only by the cycle time for the outputting of the diagnosis pulses, that is, becomes eighteen milliseconds or so for example.

[0035]According to the third or fourth aspect of the present invention, when a signal from the same input terminal of the input signal group changes the predetermined number of times consecutively, such is judged to be abnormal. Thus, even where the job site has much surrounding noise which influences on the input signals, stable safety management can be realized without being influenced by such surrounding noise. The measure like this for control stability is effective particularly at a job site where there are many use of power machineries which generate such surrounding noise.

[0043]According to the seventh or eighth aspect of the present invention, the switching operations and the circuit interruption detection operations of the circuits in executing the diagnoses are executed by the photo couplers. Because these signals are transmitted in the form of lights with a predetermined wavelength, the following advantages can be obtained.

[0045](2) It becomes possible to limit the interfaces between the circuit group on the diagnosing side and the circuit group on the diagnosed side to optical interfaces only. Thus, independencies of the both circuit groups are enhanced, so that it becomes easy to carry out circuits designs such as, for example, power circuits individually independently of one another.

Problems solved by technology

On the contrary, when the input signals from the switch SW1 and the switch SW0 of the two systems do not coincide, such is judged to be the occurrence of an abnormality, in which event an abnormality stop, that is, an emergency stop is performed to emergently stop all the output devices in a moment.

Therefore, the present situation is that it is hard to say that a required time taken to detect the abnormality such as the aforementioned short-circuit can be shortened sufficiently.

Further, since the diagnosis cycle in the cyclic diagnosis is proportional to the number of the input terminals of the input circuits, it is likely that the problem like this will increasing become prominent and actual as the system becomes large in scale.

Images